Retainer for holding a detonator in a detonator receptacle and explosive cartridge container containing the same



Oct. 29, 1968 G. L. GRIFFITH 3,407,730

RETAINER FOR HOLDING A DETONATOR IN A DETONATOR RECEPTACLE AND EXPLOSIVE CARTRIDGE CONTAINER CONTAINING THE SAME Filed Sept. 21, 1966 United States ABSTRACT OF THE DISCLOSURE This invention provides a retainer for holding a detonator in a detonator receptacle of an explosive cartridge. The retainer comprises a plurality of digital members extending across the open end of the detonator receptacle. These digital members can be a part of the end cap of the explosive cartridge or a separate component which fits into the detonator receptacle. A feature is the forming of the digital members of a hard material which can even be non-resilient, sufficient resiliency normally being imparted by the slender digital shape thereof.

This invention relates to a hard resilient digitated retainer for holding a detonator in a detonator receptacle, and to an explosive cartridge container having a detonator receptacle including such digitated means for retaining a detonator, such as a booster or a blasting cap, therein, and more particularly, to an explosive cartridge container having a detonator receptacle with a hard resilient digitated retainer partially or wholly obstructing the opening leading into the receptacle to a size smaller than the detonator, so that a detonator can be pushed past the retainer, and is thereafter held thereby within the receptacle.

Explosive cartridges that are intended to be detonated by a booster or blasting cap are usually made with a well or other receptacle into which the booster or blasting cap can be inserted. Normally, the well is open-mouthed, with no means for preventing the detonator from being accidentally dislodged, should the cartridge be inverted or should the wires lea-ding to the booster or blasting cap be momentarily snagged when the cartridge is being inserted, for example, in a bore hole or under water. Should the detonator be accidentally withdrawn from the receptacle, then, of course, the cartridge will not be fired, since it is normally essential that the detonator be in close proximity to the charge, which proximity is, of course, ensured by the placement of the receptacle in the cartridge,

Containers have been provided having means for preventing accidental withdrawal of the detonator from such receptacles. One type, as shown in French Patent No. 1,068,900 to Canis, published July 1, 1954, provides a cap which is placed over the end of the cartridge, across the open mouth of the receptacle, and which has holes through which the wires of the detonator can be threaded. Another type, described in US. Patent No. 2,993,441 to Griffith et al., dated July 25, 1961, provides a bail or handle for the explosive container, with stub ends which are spread apart in one position of the handle, permitting the detonator to be inserted into the well, and which are drawn together in another position of the handle, to partially obstruct the open mouth of the well, and prevent the detonator from being withdrawn.

US. Patent No. 2,707,437 to Noddin et al. describes a detonator whose cap well is partially closed off by a flexible rubber washer having a central perforation. Superimposed on the washer is a metal washer, likewise with a central perforation. The hard metal washer imparts rigidity to the softer rubber washer in the outward direcatent ice tion. The central perforation of the rubber washer is smaller in diameter than the blasting cap, but that of the metal washer is larger. Thus, the cap can be pushed into the well, but the metal washer prevents it from being withdrawn, the rubber washer becoming squeezed between the metal washer and the detonator if this be attempted. The device is effective, but its two-part construction makes it costly, and the two parts must be fitted together precisely, or the devices effectiveness is impaired.

In accordance with the invention, an explosive cartridge container is provided having a detonator receptacle, an opening leading into the detonator receptacle, and a hard resilient digitated retainer, the digital portions of which partially or wholly obstruct the opening in a manner such that a detonator can be forced past the retainer, to insert it into the receptacle, but will be prevented from being accidentally dislodged from the receptacle, due to the obstruction accorded by the digital members.

The invention also provides a digitated retainer as part of an end cap for an open-ended cartridge container, which fits over the detonator receptacle as well. This end cap is designed to close off the open end of the container, with an annular body portion which has this function, and it also has integral therewith an open portion that is at least partially obstructed by the digital members of the retainer. The retainer is hard, but resilient, adapted to give way under pressure of a detonator being inserted through the open portion, to permit insertion of the detonator into the receptacle beyond.

Due to the hardness of the retainer, the shape or configuration and design of the digitated members is critical, and so likewise is the extent of obstruction afforded thereby at the opening into the receptacle. The digital members are sufiiciently slender to be resilient, but hard enough to resist flexing except by application of a strong force. It is also important that the amount of free open space remaining unobstructed by the retainer be smaller than the smallest dimension overall of the detonator. The digital members should be sufficiently flexible and resilient that they can be deflected far enough to permit insertion of the detonator, and can still then return to their normal obstructing position, after the detonator has been inserted.

The retainer can, for example, take the form of an annular member having an opening therethrough with a digitated, irregularly or regularly shaped protruding periphery, with the digital portions extending into and across the opening from the periphery. The digital portions can be symmetrically or asymmetrically protruding along radii of the opening, towards the center, and partially or wholly obstructing the opening. They can also be eccentrically protruding towards an open area that is offcenter.

The member at least in the flexing portions 18 made of hard material, which can be resilient or nonresilient, sufficient resiliency normally being imparted by the slender digital shape thereof. Polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinylidene chloride, nylon, polyacrylonitrile, ethyl cellulose, cellulose acetate, aluminum, tin, and steel are suitable. The projecting or protruding digital portions can be more or less deeply indented, as desired, and according to their resiliency and the extent of the obstruction. Their length will, of course, depend upon the amount of opening that must be provided after they are flexed to permit entry of the detonator into the receptacle.

It will generally be found preferable to have at least two or three digital members, the better to obstruct the opening. Generally, it will also be found best to have the members protrude towards the center of the opening, so that the open portion through which the detonator is to be pushed is at or near the center, rather than to one side. Various forms of retainer are further illustrated in the drawings.

The digital portions of retainer are so designed that when it is desired to insert a detonator into the receptacle, the detonator is simply pushed against the digital portions, which then give way and are pushed inwardly, permitting the detonator toslide past them. The detonator will be held by frictional engagement of the digital members, if the detonator is not pushed all the way through the opening. After the detonator has been fully inserted into the receptacle, the digital portions resume their normal position. In either case, the digital members due to their rigidity resist its dislodgment. Even a temporary snag of the wires attached to a blasting cap, for example, will be insufficient to withdraw the cap from the receptacle, due to the resistance afforded by the retainer.

The digital portions of the retainer can be so placed that they extend perpendicularly to the sides of the receptacle or receptacle opening. It is preferred, however, that they extend inwardly into the receptacle, at an angle of from about 10 to about 45 inclusive to the wall of the opening, so as to further facilitate entry of the detonator, and more effectively resist its withdrawal.

In cartridges where the receptacle is in the form of a Well, inserted in an end cap of the cartridge, the retainer can be made integral with or attached to the end cap, and can even be of the same material, such as aluminum or plastic. The retainer can also be made as a washer, such as a finger washer, to fit in the opening of the receptacle. In this case or in the other case, it can also be attached to a frame which fits into the receptacle, or is made a part of the receptacle structure. Those skilled in the art will perceive other adaptations, from this description.

For greater resiliency at their ends, the flexing portions of the retainer can be made tapered, so as to be thin at their periphery, and thick at their base.

The invention is applicable to receptacles of all types for use with detonators, such as boosters or blasting caps. The receptacle can take any form, and can be of any dimensions, according to the requirements of the cartridge, and can be attached at the outside of the cartridge as well as within the cartridge, as in the form of a well. The cartridge can be used with any type of explosive charge.

A primer will be filled with a high explosive charge. Any high explosive can be used, such as trinitrotoluenesensitized ammonium nitrate-type slurry high explosives, smokeless powder-sensitized ammonium nitrate-type slurry high explosives, nitrostarch-sensitized ammonium nitrate-type slurry high explosives, trinitrotoluene-sensitized ammonium nitrate pellet form solid high explosives, and nitrostarch-sensitized ammonium nitrate-type semisolid high explosives, nitrocarbonitrates, nitroglycerine dynamites, such as semi-gelatin, ammonia gelatins, and ammonia dynamites.

A primer cartridge can include a booster explosive in close juxtaposition to the high explosive, in which case the receptacle may be placed in or in juxtaposition to the booster. A booster cartridge will contain only a booster explosive, and the receptacle. Any booster explosive can be used, such as Pentolite, ammonium dynamite, nitroglycerine dynamite, nitroglycerine, semi-gelatin and gelatin dynamites, Composition B, RDX, and pentaerythritol tetranitrate.

The drawings represent preferred embodiments in the opinion of the inventor of explosive cartridges including a detonator receptacle and a retainer in accordance with the invention.

FIGURE 1 is a top view of a circular end cap for closing off the open end of a cylindrical cartridge, and embodying a digitated retainer according to the invention.

FIGURE 2 is a cross-sectional view of the cartridge of FIGURE 1, showing a blasting cap in position in the well thereof.

The retainer of- FIGURES 1 and 2 is an integral porttion of an end cap of a cylindrical explosive cartridge. The end cap 1 is made of plastic material, such as polypropylene, which is hard but has a certain resiliency when in the form of a slender strip, and is molded in one piece with a central opening 2 intended to fit over the open well of a blasting cap receptacle. Into the open portion 2 from the periphery thereof extend six fingers 3, regularly positioned along radii of the opening towards the center, at 30 intervals. In the device shown, the fingers stop short of the open center 2, leaving an'opening of an inch in diameter. The total diameter of the opening 2 is inch. Thus, the fingers extend about onehalf the length of their radii towards" the center. As is best seen in FIGURE 2, the fingers 2 also extend inwardly at an angle of about 45 to the side wall of the well 4.

FIGURE 2 shows the position of the end cap across the open top of the well 4, with a blasting cap 5 in posi tion in the well, closing off the open end of the rigid poly-- propylene cartridge 8. The wires 6' of the blasting cap 5 extend out through the opening 2.

It is evident from FIGURE 2 that the open space beyond the inner ends of the fingers 3 has a lesser diameter than that of the blasting cap, and that the cap is accordingly retained in the well by the fingers.

The blasting cap is readily inserted in the well, simply by pushing it past the fingers 3. These give way under the pressure of the cap, but spring back into the position shown in FIGURE 2, after the cap has been fully inserted in the well.

Alternatively, a longer cap can be used, in which case the fingers engage the sides of the cap after the cap has been inserted, and is held in the well by such frictional engagement with the fingers.

The end cap 1 is integrally bonded to the side walls 2 of the cartridge container 8 by heat and pressure. The cartridge can be filled with any suitable explosive. In the instance shown, the explosive cartridge is a booster, and the booster explosive is a nitrocarbonitrate. The other open end of the cartridge tube is closed off by an end cap 11, inserted in the open end of the tubing and bonded thereto in like manner as cap 1.

It will be evident that the container of the invention is applicable to any type of explosive cartridge including a receptacle for a detonator, such as a booster or blasting cap. The drawings show various ways in which the retainer can be attached across the open end of the receptacle, but other variations will be apparent to those skilled in this art, from the preceding description.

Having regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. An end cap for an explosive cartridge container, adapted to close off both an open end of the container and an open-ended detonator receptacle disposed therein, comprising an annular body portion for closing oif a corresponding annular open end portion of the container surrounding the detonator receptacle and an open portion defined by the annulus and arranged to fit over the open end of the receptacle, with a detonator retainer of hard material extending over and at least partially obstructing the open portion, reducing it to an open area smaller than the smallest dimension of a detonator to be retained thereby in the receptacle, the retainer having a plurality of digital members facing the open portion and said digital members being of sufiiciently narrow width so as to be resilient so that the members give way under pressure of a detonator being inserted through the open portion into the receptacle.

2. An end cap in accordance with claim 1, wherein the end cap annular portion and the retainer are in one piece.

3. An end cap in accordance with claim 2, wherein the end cap and retainer are made of nonresilient plastic material, but have a sufiicient resiliency due to the digital sha e.

4 An end cap in accordance with claim 1, in which the digital members are adapted to flex during insertion, and to return to normal position after insertion of the detonator through the open portion into the receptacle, thereby to retain the detonator in the receptacle.

5. An explosive cartridge container having a detonator receptacle, an opening in the receptacle for insertion of a detonator thereinto, and a detonator retainer of hard material positioned across and at least partially obstructing the opening, reducing it to an open area smaller than the smallest dimension of a detonator to be retained thereby in the receptacle, the retainer having a plurality of digital members facing the open portion and said digital members being of sufliciently narrow width so as to be resilient so that the members flex and thereby permit insertion of a detonator therepast into the receptacle, and return to their normal position to retain the detonator in the receptacle thereafter.

6. A container in accordance with claim 5, wherein the receptacle is in the form of an openended well extending into an explosive charge contained in the container.

7. A container in accordance with claim 5, wherein the retainer comprises a finger washer member fitted over the open end of the wall,

8. A container in accordance with claim 5 wherein the retainer is an integral part of an end cap closing off an open end of the container.

9. A container inaccordance with claim 8, in which 1 the retainer and end cap are made of plastic material.

10. A container in accordance with claim 9, in which the plastic materialjs nonresilient, but the digital members have a sufiicient resiliency due to the digital shape.

11. A container in accordance with claim 5, wherein the digital members also extend inwardly into the receptacle at an angle between about 10 and about 45 to the wall thereof.

References Cited BENJAMIN A. BORCHELT, Primary Examiner. V. R. PENDEGRASS, Assistant Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,407,730 October 29, 1968 George L. Griffith It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 6, "insertion" should read insertion, Column 6, line 2, "wall" should read well j..

Signed and sealed this 7th day of April 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

